In various types of communication systems, electromagnetic interference may cause problems with the operation of the communication system. Generally, electromagnetic interference is a disturbance that can affect the operation of a circuit due to electromagnetic induction or electromagnetic radiation emitted from an external source. In a communication system, electromagnetic interference may cause the degradation or loss of data. Exemplary sources of electromagnetic interference include other electronic devices, undesired wireless signals, radio jamming signals, as well as natural phenomenon.
One example of a radio-frequency interference (RFI) suppression technique is described in U.S. Pat. No. 5,742,900 (Arnstein, et al.), which is incorporated by reference herein. In this example, a biased inverting limiter is used to reduce interference. This example requires two signal paths; one path to estimate the amplitude envelope of the interference signal, and a second path to process with the nonlinear biased inverting limiter acting as the “amplitude trap”. A carefully calibrated bulk delay line and compensating linear amplifier are required in the second, nonlinear processing path to match the group delay of the control path.
The requirement of a delay element in the nonlinear RF signal path is problematic for implementation, as is the linear booster amplifier to compensate for the attenuation inherent in practical delay elements. In an interference environment, linear amplifiers early in the receiver signal chain are already vulnerable to saturation or undesirable nonlinear effects.